Graduate Students on Biodiversity Science

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It’s the end of the year and that means that it’s time for our 2013 link dump, where we highlight our favorite research (and other stuff) in biodiversity in 2013. If you think there’s something we missed, or have something to say, please share in the comments section!

Last December*, 121 researchers from across the globe put their best estimates of marine biodiversity to paper, giving us “The Magnitude of Global Marine Species Diversity” (Pop-POP). The article in Current Biology represented a comprehensive baseline estimate of how many species live in the ocean, broken down by phyla. According to the authors, approximately 700,000 – 1,000,000 species live in the ocean, with only about half of them discovered and described. That means that if we discovered a new marine species each day, it would take us over 1,350 years to collect them all. In comparison, it only took me four months and most of my social life to do the same thing in Pokemon Red. Anyway, the good news is that despite the many threats that face our oceans, they still hold an incredible amount of biodiversity waiting to be discovered. Years from now, when both Pitbull and the duck face no longer exist, we’ll still be finding new species on our planet. Sounds good to me. - Nate Johnson

Hundreds of new species were discovered in 2013. Several other sites have developed lists (see here for Amazonian examples, here for California Acadamy of Science’s haul, and here for Time’s take) but my personal favorites are:

During my interview with Dan Simberloff earlier this month (stay tuned for the full post!), he lamented that there wasn’t enough publicity of good news in invasion management, because, well, good news doesn’t sell. But [SPOILER ALERT/SNEAK PREVIEW] he offered to highlight two recent bits of good news in control and eradication of invasive species:

Melaleuca (Australian paper bark) control efforts in Florida. Dr. Simberloff worked for many years in South Florida and, this year, on visits, observed that the intensive control efforts (spraying, prescribed burns) were paying off, dramatically reducing the area dominated by the species and showing evidence of recovery of native vegetation.

Development and implementation of genetic techniques for controlling invasions such as: The Daughterless Carp Program and projects releasing genetically modified mosquitos on small islands to act as reproductive sinks.

Next up: Reports from Deep Time – Dead biodiversity!: 2013 saw some ridiculous new fossil discoveries (thanks to Brandon Peecook, fossil aficionado, for the following hit parade):

Fossil pollen indicates flowering plants evolved 100 million years earlier than previously thought (252 – 247 MYA). That dramatically changes the concept of what the set should look like on Jurassic Park, and even Triassic Park, and of course our attempt to understand the ecology of those periods.

NEW SPECIES of rad/terrifying Cambrian proto-arthropod named after Johnny Depp because it looks like Edward Scissorhands (I guess scissorhandsensis doesn’t roll off the tongue). Thanks to Vicinius for the link to the report on Kooteninchela deppi.

Enormous camels used to live in the boreal forest?! What will they think of next?! Bring ‘em back!

A lot cool things came out in 2013! We learned new things about old issues, and that is exciting! We still have a lot to learn about topics that have been around for over 200 years (see below)!!! We also witnessed new advancements in some unexplored areas. Here are some of my highlights:

Carlos Botero and colleagues published an exciting work titled “Environmental harshness is positively correlated with intraspecific divergence in mammals and birds”. Their results shed new light into one of the most enduring topics in Ecology and Biogeography, the Latitudinal Diversity Gradient (LDG) and propose a new explanation to this old issue: The LDG occurs as a consequence of higher species turnover in temperate zones. They show that, contrary to our common knowledge, speciation rates are much higher in temperate zone than in the tropics, perhaps as a consequence of harsh weather, which eventually exterminate some populations, but not the entire species, creating geographical isolation among the surviving populations, and promoting divergence. Higher speciation rates combined with higher extinction rates cause species to replace each other more frequently in higher latitudes than in lower ones. Based on their findings, it seems that the tropics harbor higher biological diversity because species tend to accumulate over time and not because they speciate at greater rates (A post giving more details about this paper should be coming out soon. Stay tuned!).

Species coexistence is another longstanding theme in ecology that has received new insights in the past year. Some of the pillar of the coexistence theory are the interrelated concepts of Limiting Similarity and Character Displacement, that is, the idea that natural selection would favor the evolution of traits that would lessen resource competition among species as two, or more, species competing for the same resources cannot stably coexist. These concepts remain widely accepted by community ecologists, despite some good evidences against it (see for instance Mayfield & Levine and the post written by Jeremy Fox).

Among the papers that came out past year challenging these accepted views are the work of Keith J. Fritschie et al., titled “Evolutionary history and the strength of species interactions: testing the phylogenetic and limiting similarity hypothesis.” Fritschie et al. tested the phylogenetic limiting similarity hypothesis using algae as models organisms in a microcosm experiment. Surprise, surprise, they found no relationship, whatsoever, between competitive strength and phylogenetic resemblance. They suggest that the biological factors driving competition are, most likely, not evolutionarily conserved, and that “ecologists may need to re-evaluate the previously assumed generality of the limiting similarity hypothesis” (Jon wrote a piece, with much more detail about this paper here).

Another excellent study challenging these classical views is a Nature paper, authored by Joseph A. Tobias and colleagues, titled “Species coexistence and the dynamics of phenotypic evolution in adaptative radiation”. This one just came out and is really exciting! This seems to be the first study on coexistence to explicitly consider the evolutionary age of species (see a good text about it here). The authors examined trait divergence in relation to interactions among 350 lineages of ovenbirds and estimated divergence in functional traits associated with competition. Once again, the results seem to be in disagreement with the conventional wisdom that coexistence promotes trait divergence among co-occurring species! Divergence seems to be best predicted by evolutionary age, suggesting that most trait differences among lineages accumulate over evolutionary time as a result of processes such as genetic drift and ecological adaptation. Coexisting species are actually more similar than species evolving separately, once the evolutionary age of species are accounted for. The authors go further and conclude: “macro-evolutionary patterns previously interpreted as character displacement should be re-analyzed in an explicitly temporal framework, as doing so may show that mechanisms of character convergence are widespread”.

An exciting new area that was explored in 2013, is what Lázló Orlóci called “Quantum Ecology” (i.e., the study of the potential energy structure of biological communities and its environmental and evolutionary determinants); throughout the year I found five manuscripts that incorporate some of the principles of Quantum Physics into Ecology and Evolutionary Biology that are really worth reading:

At last, the special issue of The American Naturalist dedicated to the interplay of evolutionary and ecological dynamics, titled “A Critical Look at Reciprocity in Ecology and Evolution” is an excellent collection of theoretical and empirical studies dealing with the feedback between ecological and evolutionary dynamics, across different levels of biological organization. Excellent reading and, certainly important for population and community ecologists and evolutionary biologists!

The “largest” zoological discoveries of this century (literally speaking, as these animals weigh over a 100 kg!): a new Tapirus species (Tapirus kabomani) and a new humpback dolphin species within the genus Sousa

At last, 15 new bird species were recently described for the Amazon Forest. Their description appeared in a special volume of the Handbook of the Birds of the World (here is an article in Portuguese).

And finally, and sadly, here is a list, compiled by Dr. David Steen, of some of the animals that were declared extinct last year.

- Vinicius Bastazini

I’m tempted to call 2013 the year of the dilution effect in disease ecology. The year started off strong with a thoughtful review (technically in 2012) by Ostfeld and Keesing on the Effects of host diversity on infectious disease in Annual Review of Ecology, Evolution, and Systematics. They essentially set out to explain why we don’t always see a dilution effect even though we might expect it. This was followed up by Johnson et al 2013, in Nature, who argued that species poor communities tend to be dominated by the most competent hosts, driving an apparent dilution effect at high host diversity. So ecologists were working towards a mechanistic explanation of the dilution effect, which is fantastic. Then a meta-analysis by Salkeld et al suggested that the dilution effect is idiosyncratic at best, and a zombie idea at worst. This was then followed by a review by Chelsea Wood and Kevin Lafferty in TREE that suggests that one reason for seemingly contradictory results is the scale-dependence of the diversity-disease relationship.

ESA had an abundance of presentations on the dilution effect, too. My favorite was this presentation by graduate student Alex Strauss from Indiana University. Using a combination of modeling and experiments, he demonstrated a wide range of potential outcomes when competitors are added to a system. Some were consistent with the dilution effect and some weren’t.

Parasite Ecology (easily my favorite new blog of 2013) tackled the dilution effect in two posts here and here. I think the conclusions are a little overly black and white (e.g., who wins and loses the dilution effect debates), but it’s a thoughtful review of the ongoing debate.-Fletcher Halliday

31 December, 2013

*I’m aware that technically this came out in 2012, but I assume most people were too preoccupied with Mayan calendars to read it until January.

This material is based upon work supported by the National Science Foundation under Grant No. DEB-1050680. Any opinions, findings, and conclusionsor recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.